The influence of recurrent EBV BRLF1 expression on genetic copy number alterations

The EBV BRLF1 expression may exert an influence on genome instability. To test this speculation, the long-term experiment of recurrent BRLF1 expression was performed. The NPC cells (TW01-TetER, doxycycline inducible BRLF1 expressing cell line) were used. Experimental samples were derived from different passages of the NPC cells without or with BRLF1 expression. Array CGH (aCGH) was carried out to investigate the copy-number aberrations in response for different frequencies of BRLF1 expression. Compared to P1 as a common reference, a dramatic increase of aberrations was observed in R15 especially on chromosomes 3, 4, 5, 6, 7, 11, 12, 13, 14, 15, 16, 17 and 21. However, relatively few aberrations were detected in R1. Under long-term cell culture, P15 was not observed obviously changed in terms of aberrations. According to the results, recurrent expression of BRLF1 may be critical in inducing aggravated genome instability in NPC cells. Samples of four sources (P1, P15, R1 and R15) were analyzed. The NPC cells were seeded. After seeding for 24 h, the cells were mock or treated with 50 ng/ml doxycycline for 24 h. After incubation for 24 h, the cells were recovered by replacing with fresh medium and incubated for 24h. The resulting cells were defined as passage 1 (P1) or BRLF1 expression 1 (R1). The procedure was repeated for 15 rounds and the resulting cells were defined as passage 15 (P15) or BRLF1 expression 15 (R15). Genomic DNA from passage 1 (P1) of NPC cells was used as controls. Genomic DNAs extracted from P15, R1 and R15 cells were used as experimental samples and subjected to Cy5-labeling reactions. Genomic DNAs extracted from P1 cells were used as the common reference sample subjected to Cy3-labeling reactions.